Contact enhancement apparatus for an electric switch

Abstract

A contact enforcement apparatus for an electric switch includes two electro-magnetic bars. The first electro-magnetic bar is disposed between a crossbar of the switch and a moveable contact arm. The crossbar carries the moveable contact arm and the first electro-magnetic bar such that the electrical contacts of a stationary contact arm and the moveable contact arm are opened and closed by the crossbar. The second electro-magnetic bar is in U-shape and has a front wall and a back wall, between which the moveable contact arm is at least partially inserted when the electrical contacts are closed together. When a "fault" current passes by the electrical contacts, an attractive force between the electro-magnetic bars is largely increased. This attractive force overcomes a repulsive force caused by the "fault" current which tends to open up the electrical contacts, so that the contact between the moveable and stationary contacts remain closed.

What is claimed is: 
     
       1. A contact enhancement apparatus for an electric switch, comprising: a stationary contact arm having at least one electrical contact;   a moveable contact arm having at least one electrical contact, the electrical contacts of the moveable and stationary contact arms being electrically connectable to each other;   a crossbar carrying the moveable contact arm and lifting and lowering the moveable contact arm such that the electrical contacts of the stationary and moveable contact arms are connected and disconnected to and from each other by the crossbar;   a spring being disposed between the moveable contact and the crossbar, the moveable contact arm being spring-biased toward the stationary contact arm by the spring when the electrical contacts of the moveable and stationary contact arms are connected to each other;   an electro-magnetic bar being disposed in sandwich between the crossbar and the moveable contact arm, such that the electro-magnetic bar is lifted and lowered along with the crossbar and the moveable contact arm; and   a U-shaped electro-magnetic bar being horizontally spaced apart from the stationary contact arm, the moveable contact arm being at least partially insertable inside the U-shaped electro-magnetic bar when the electrical contacts of the moveable and stationary contact arms are connected to each other, an air gap being formed between the electro-magnetic bar and the U-shaped electro-magnetic bar.   
     
     
       2. A contact enhancement apparatus according to claim 1, wherein the air gap is about 1 millimeter (mm). 
     
     
       3. A contact enhancement apparatus according to claim 1, wherein the electro-magnetic bars are made of iron. 
     
     
       4. A contact enhancement apparatus according to claim 1, wherein the moveable and stationary contact arms are made of copper. 
     
     
       5. A contact enhancement apparatus according to claim 1, wherein the electrical contacts of the moveable and stationary contact arms are made of Silver Graphite. 
     
     
       6. A contact enhancement apparatus for an electric switch, comprising: a stationary contact arm having at least one electrical contact;   a moveable contact arm having at least one electrical contact, the electrical contacts of the moveable and stationary contact arms being electrically connectable to each other;   a crossbar carrying the moveable contact arm and lifting and lowering the moveable contact arm such that the electrical contacts of the stationary and moveable contact arms are connected and disconnected to and from each other by the crossbar;   a spring being disposed between the moveable contact and the crossbar, the moveable contact arm being spring-biased toward the stationary contact arm by the spring when the electrical contacts of the moveable and stationary contact arms are connected to each other;   a U-shaped electro-magnetic bar being disposed between the crossbar and the moveable contact arm, the U-shaped electro-magnetic bar being lifted and lowered along with the crossbar and the moveable contact arm, the moveable contact arm being disposed inside the U-shaped electro-magnetic bar; and   a second electro-magnetic bar being horizontally spaced apart from the stationary contact arm, an air gap being formed between the second electro-magnetic bar and the U-shaped electro-magnetic bar.   
     
     
       7. A contact enhancement apparatus according to claim 6, wherein the air gap is about 1 millimeter (mm). 
     
     
       8. A contact enhancement apparatus according to claim 6, wherein the electro-magnetic bars are made of iron. 
     
     
       9. A contact enhancement apparatus according to claim 6, wherein the moveable and stationary contact arms are made of copper. 
     
     
       10. A contact enhancement apparatus according to claim 6, wherein the electrical contacts of the moveable and stationary contact arms are made of Silver Graphite.